The present invention relates generally to bicycle transmissions and, more particularly, to an internal transmission device which automatically shifts gears in accordance with rotation of the hub components.
It is sometimes difficult to start pedaling a bicycle from a resting position, because riders often leave the bicycle in a relatively high gear when parking the bicycle, forgetting to shift to a lower gear. To solve this problem, two types of solutions have been proposed. One is an electrical solution and the second is a mechanical solution. Electrical solutions typically include a motor, electrical circuitry, a battery and a control device with a shifting mechanism. The control device electrically shifts into a low gear ratio when the bike is stopped. But this solution is expensive and the rider has to change batteries often.
Most mechanical solutions involve a centrifugal force mechanism in the hub that sets the gear ratio at a low gear when the bike is stopped and changes the gear ratio after a predetermined wheel speed is reached. U.S. Pat. No. 3,603,178 shows a bicycle equipped with an internal shifter hub wherein the gear ratio may be shifted automatically in accordance with centrifugal force created by the rotating wheel. Such an internal shifter hub comprises a hub axle, a driver capable of rotating about the hub axle, a hub shell, a planet gear mechanism for changing the speed of rotation of the driver and transmitting the result to the hub shell, a clutch mechanism for transmitting the output of the planet gear mechanism to the hub shell or stopping such transmission, a clutch-switching mechanism for switching the clutch mechanism by centrifugal force, and a support sleeve disposed between the planet gear mechanism and the hub shell.
The planet gear mechanism comprises an inner-tooth gear, a sun gear, a plurality of planet gears for meshing with the inner-tooth gear and the sun gear, and a planet gear carrier for supporting the plurality of planet gears. The planet gear carrier is formed integrally with the driver. The support sleeve is rotatably supported on the hub axle and is joined by a serrated joint with the planet gear carrier. A one-way clutch is mounted between the support sleeve and the hub shell.
The clutch mechanism has a ratchet pawl disposed between the inner-tooth gear and the hub shell, links the two when the ratchet pawl is in an engaged position, and disengages the two when the ratchet pawl is in a disengaged position. The hub shell is driven in an up shift mode via the planet gear mechanism when the clutch mechanism is in the engaged position, and the hub shell is driven while being directly linked to the driver when the ratchet pawl is in the disengaged position.
The clutch-switching mechanism comprises a weight member that swings by centrifugal force and a control member that rotates in response to swinging of the weight member. The weight member and control member are mounted on a weight support, itself mounted rotatably on the support sleeve. The weight support is nonrotatably linked to the inner-tooth gear.
The control member uses circular movement to switch the ratchet pawl of the clutch mechanism between the engaged position and the disengaged position. An upright control pin for interlocking with the control member is provided with a slit for interlocking with the control pin and with a control hole for controlling the clutch pawl. The interlocking of the control pin and slit converts the rocking movement of the weight member into the circular movement of the control member.
In such a conventional internal shifter hub, the ratchet pawl of the clutch mechanism is kept by the control hole of the control member in a position in which the pawl is separated from the hub shell until a rotational speed promoting the outward swinging of the weight member is reached. During this time, rotation transmitted from the sprocket to the driver is transmitted from the carrier to the hub shell via the support sleeve and the one-way clutch, and the hub shell is driven in a direct-coupled mode. When a certain rotational speed is achieved and the weight member has swung outward, the control pin turns while sliding in relation to the slit and causes the control member to rotate. When this happens, the ratchet pawl, controlled by the control hole, rises to the engaged position in which it is interlocked with the hub shell. In this state, the rotation that has been transmitted from the sprocket to the driver is upshifted and outputted from the carrier to the inner-tooth gear via the planet gears, and is further transmitted to the hub shell via the clutch mechanism, thus driving the hub shell in to an upshifted mode.
In this arrangement wherein the clutch mechanism is switched and the speed is changed using centrifugal force, the extent of rocking of the weight member is very small because the weight member has a limited housing space. Additionally, the control pin has a short revolution path in relation to the rocking of the weight member because the control pin is disposed in the vicinity of the center of rocking of the weight support. The control member is therefore unable to rotate over significant distances, making it necessary that the ratchet pawl be switched between the engaged position and the disengaged position by a very small amount of circular movement.
Another drawback is that large centrifugal forces are difficult to obtain because of the limited housing space for the weight member. It is therefore necessary to increase the efficiency with which the rocking movement is converted to a circular movement in the clutch-switching mechanism. With the conventional arrangement described above, however, the efficiency with which the rocking movement is converted to a circular movement is low, the circular movement of the control member is impeded in relation to the rocking of the weight member, and smooth shifting is difficult to achieve because the control pin interlocked with the slit must slide along the slit to convert the rocking movement of the weight member into the rotational movement of the control member.
Accordingly, it is desirable to provide an interior shift device for a bicycle that is simple in construction, lightweight and overcomes the disadvantages of the prior art.
In accordance with a first aspect of the present invention there is provided an internal transmission device for a bicycle. The device includes a slave member, a driver, a planetary gear mechanism disposed between the driver and the slave member, and an automatic shift control mechanism actuated relative to a rotational angle of the driver in a driving direction. The automatic shift control mechanism includes a first one way clutch, a clutch control member and a first abutment member that is disposed on the inner peripheral surface of the slave member.
In a preferred embodiment, the automatic shift control mechanism also includes a second abutment member disposed on the inner peripheral surface of the slave member. The second abutment member is preferably adjacent to and staggered with the first abutment member. The first abutment member is positioned to be engaged by the first one way clutch and the second abutment member is a positioned to be engaged by the clutch control member. In a preferred embodiment, the clutch control member comprises a clutch cage, such as a pawl cage, and is rotatable relative to the planetary gear mechanism and is also rotatable with the slave member. Preferably the clutch control member has an end that is bent radially outwardly. In operation, a tip end of the first one way clutch preferably rotates in a direction opposite to the driving direction. The planetary gear mechanism may be disposed radially inwardly of the slave member or the driver/ring gear, or it may be disposed laterally adjacent to the slave member.
In another preferred embodiment, the device includes an axle and a clutch body that is rotatable about the axle and movable in an axial direction. The clutch body may include a key member and be externally operated by a push rod and may be positioned in at least first, intermediate and second positions, wherein the gear ratio is fixed when the clutch body is in the first position, the gear ratio is automatically changed from a low gear ratio to a middle gear ratio in the intermediate position, and wherein the gear ratio is automatically changed from a middle gear ratio to a high gear ratio in the second position.
The automatic shift control member may be actuated relative to the rotational angle of the driver in the driving direction with different rotational angles between the ring gear and the slave member.
In accordance with another aspect of the present invention there is provided an internal transmission device for a bicycle. The device includes a hub axle having a sun gear formed integrally therewith, a driver rotatably mounted to the hub axle, a slave member rotatably mounted to the hub axle and rotatable independently of the driver, a planet gear mechanism, and an automatic shift control mechanism that is actuated when the slave member rotates relative to the driver a predetermined rotational angle xcex8. The driver includes a first clutch pawl pivotably mounted thereon that pivots between an engaging position and a disengaging position. The slave member has a set of teeth formed on an inner surface thereof. The planetary gear mechanism includes a ring gear having first and second sets of inner teeth, a planet gear, and a carrier rotatably mounted on the hub axle and carrying the planet gear. The planet gear is disposed between the sun gear and the second set of teeth on the ring gear and the carrier has a second clutch pawl pivotably mounted thereon for engaging the set of teeth on the inner surface of the slave member. The automatic shift control mechanism includes a third clutch pawl mounted on the ring gear, a clutch control member having an end that is bent radially outwardly and that includes a notch defined therein, and a first abutment member disposed on the inner peripheral surface of the slave member.
In accordance with yet another aspect of the present invention there is provided a method of power transmission in a bicycle component. The method includes the steps of rotationally powering a driver, wherein the driver rotationally powers a ring gear, wherein the ring gear rotationally powers a planet gear carrier, wherein the planet gear carrier rotationally powers a slave member, actuating an automatic shift control mechanism by engaging a first one way clutch on the ring gear with the slave member, and wherein the first one way clutch rotationally powers the slave member independently of the planet gear carrier. The automatic shift control mechanism is actuated relative to a rotational angle of the driver in the driving direction.
In accordance with yet another aspect of the present invention there is provided an internal transmission device for a bicycle including an axle, a slave member rotatably mounted to the axle, a driver rotatably mounted to the axle, the driver for transmitting power to a ring gear, a clutch control member, a planet gear mechanism including a planet gear carrier, an automatic shift control mechanism that is actuated relative to a rotational angle of said driver in a driving direction, a low gear configuration wherein the ring gear transmits power to the slave member through the planet gear carrier, and a high gear configuration wherein the ring gear transmits power directly to the slave member.
In accordance with yet another aspect of the present invention there is provided an internal transmission device for a bicycle including a driver, a slave member having a first portion, a planetary gear mechanism disposed between the driver and the first portion of the slave member, and an automatic shift control mechanism actuated relative to a rotational angle of the driver in a driving direction. The automatic shift control mechanism includes a first one way clutch, a clutch control member and a first abutment member. The clutch control member partially surrounds and is rotatable independent of the first portion of the slave.
In accordance with yet another aspect of the present invention there is provided an internal transmission device for a bicycle comprising including an axle, a slave member rotatably mounted to the axle, a driver rotatably mounted to the axle, a planetary gear mechanism disposed between the driver and the slave member, a clutch body movable in an axial direction and positionable in at least first, intermediate and second positions, and an automatic shift control mechanism actuated relative to a rotational angle of the driver in a driving direction. The automatic shift control mechanism comprises a first one way clutch, a clutch control member and a first abutment member. The automatic shift control mechanism is not actuated when the clutch body is in the first position. The automatic shift control mechanism shifts between a low gear ratio and a middle gear ratio when the clutch body is in the intermediate position. The automatic shift control mechanism shifts between a middle gear ratio and a high gear ratio when the clutch body is in the second position.
Other objects, features and advantages of the present invention will become apparent to those skilled in the art from the following detailed description. It is to be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the present invention, are given by way of illustration and not limitation. Many changes and modifications within the scope of the present invention may be made without departing from the spirit thereof, and the invention includes all such modifications.